Vacume leaks The AC controls inside the car go from the floor outlets to the defrost position when you put a load on the car during acceleration. The manifold for the up and down motion has been changed. The engine manifold, all three parts has been changed, but no luck. The ac still will not blow out the vents except at slow speeds and the engine is running rough. divescubatime@gmail.com

I just bought this van used and it is doing exactly the same thing. The engine runs fine, but when stepping on the accelerator to enter traffic, climb hills, etc. the fan switches to blow out the defrost vents until the engine returns to a normal running condition.

Please help, as this really annoys me!!!I just bought this van used and it is doing exactly the same thing. The engine runs fine, but when stepping on the accelerator to enter traffic, climb hills, etc. the fan switches to blow out the defrost vents until the engine returns to a normal running condition.

You have a vacuum leak look under the hood on the passenger side at the fire wall check the two hoses there follow them to see if they are bad find the vac canister looks like a ball see if there not bad there may be under left fender

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it could be a bad switch... it could also be leaking vacum lines (vacum is what operates the dirictional doors). it could be a stuck door, or bad hinge. it could also be loose ducts underneath the dash.

Interesting. If it is a vac leak you should be able to plug the line from the intake to kill the leak.My guess would be the idle speed control is raising the base idle to cover the load the ac compressor would put on the engine.If the compressor is not working, the computer would not know.

When the gas petal is pushed down the engine needs a amount of vacum to run.If there is not enough vacum it will pull vacum off heater/ac box inside which controls where the ai flow is controled.Check intake for vaccum leaks,hoses,connections.look for vaccum lost.

There could be a vac tank problem or a vac leak.Most american vehicles use a plastic ball or object as a vac holding tank. The tank or a vac hose can be leaking.If the system fails, the default position is the defrosters for safety.

The air flow is controlled by vacum. I would start by inspecting all the hard plastic vacum lines under the hood. If you find none broken or loose , then inspect the control panel. by "default" the air is derected to the defrost position.

The air direction is vacum controlled. If you have 4X4 and ESOF ( switch in the cab) then you need to inspect the vacum lines that go to the hubs and possibly the hub seals. "default" position for air flow is the defrost position. If you DON'T have 4X4, and it's a diesel engine, inspect the vacum pump, If it's a gas engine then look at all the vacum lines from the intake manifold for a leak.

Not sure what you mean by loss of power. If you mean lack of acceleration or bogging down, than a bad cat convertor can cause this problem because you are lossing vacuum during acceleration causing the vents to switch from floor to defrost. Hope this helps leave comment.

u have a loss of vacuum to the ac mode control switch, this switch applies vacuum to diff vacuum motors to move air to diff outlets, dash, floor, defrost etc. either the vacuum line or vacuum resivior at the engine is leaking or the mode control is leaking vacuum.